Hi Rajesh,I didn't do any photo-reference for the study in this case. I did however, have a particular person in mind when I did the face. Sometimes I will use a mirror and my own expressions for a certain look. Other times I may try to remember the look on someone's face, which is what I did here.

I draw all my drawings traditionally. The only point that I may draw digitally is if I need to correct something really glaring in a drawing. In which case I scan the image into Photoshop, adjust as necessary, print the image back out, transfer a basic outline the new design it to a new sheet of paper, and redraw it all over again.